Crystals in synthetic urine?

I had a little bit of advanced notice for a piss test so I checked my synthetic urnine sample as in the past I have had problems with certain products. It had some clear tiny crystals at the bottom of the bottle and a couple of small fluffy material as well. I was able to run it through a strainer and got most of it out, but I was wondering what the hell that is.
Same thing happened when I tried to use a bottle of X-factor brand synthetic. This one is Rockstar Piss brand. I don't think it would look too cool with these things when the lab pours from the cup into the split sample vials. Anyone know what this is and anyone had similar experience?
I was able to get a clean sample from my ex and will be using that instead.
Cheers.